Room: AAPM ePoster Library
Multi-lumen and segmented cylinder applicators of the same diameter differ in their overall design especially as it relates to the dome of the applicator and their assembly. The purpose of this project is to compare the dose distribution between multi-lumen and segmented cylinders of 25mm, 30mm, and 35 mm when delivering identical treatment plans.
A single lumen treatment plan using an Ir-192 source was created for each cylinder with 9 dwell positions and 30 seconds dwell time for each position. The decay of the source was automatically accounted for by the treatment console for each delivery. Measurements for the dome of 25mm, 30mm, and 35mm multi-lumen and segmented single-lumen cylinders were collected at 0°, 30°, and 45° on the surface and at 5mm depth at 0° using a PTW 13343 Markus parallel-plate ion chamber. The measurements at each point on the multi-lumen cylinder were compared to the segmented cylinder of the same size. Then the dose profile along the side at the midline of each cylinder was collected using EBT-3 gafchromic film. The dose profiles were analyzed using 2mm/3cGy gamma analysis and a gamma tolerance of 1 in RIT software.
The 25mm cylinders agreed within 2.1% for each position on the dome and had a gamma analysis passing rate of 96.6% along the sides of the cylinder. The 30mm cylinders agreed within 3.5% for each point on the dome and had a gamma analysis pass rate of 99.5% along the sides of the cylinder. The 35mm cylinders agreed within 1.6% at each point on the dome and had a gamma analysis pass rate of 98.4%.
Overall, the dose distribution of each cylinder size showed close agreement between the two types of cylinder applicators.